title: Novel Burkholderia mallei virulence factors linked to specific host-pathogen protein interactions.
abstract: Burkholderia mallei is an infectious intracellular pathogen whose virulence and resistance to antibiotics makes it a potential bioterrorism agent. Given its genetic origin as a commensal soil organism, it is equipped with an extensive and varied set of adapted mechanisms to cope with and modulate host-cell environments. One essential virulence mechanism constitutes the specialized secretion systems that are designed to penetrate host-cell membranes and insert pathogen proteins directly into the host cell's cytosol. However, the secretion systems' proteins and, in particular, their host targets are largely uncharacterized. Here, we used a combined in silico, in vitro, and in vivo approach to identify B. mallei proteins required for pathogenicity. We used bioinformatics tools, including orthology detection and ab initio predictions of secretion system proteins, as well as published experimental Burkholderia data to initially select a small number of proteins as putative virulence factors. We then used yeast two-hybrid assays against normalized whole human and whole murine proteome libraries to detect and identify interactions among each of these bacterial proteins and host proteins. Analysis of such interactions provided both verification of known virulence factors and identification of three new putative virulence proteins. We successfully created insertion mutants for each of these three proteins using the virulent B. mallei ATCC 23344 strain. We exposed BALB/c mice to mutant strains and the wild-type strain in an aerosol challenge model using lethal B. mallei doses. In each set of experiments, mice exposed to mutant strains survived for the 21-day duration of the experiment, whereas mice exposed to the wild-type strain rapidly died. Given their in vivo role in pathogenicity, and based on the yeast two-hybrid interaction data, these results point to the importance of these pathogen proteins in modulating host ubiquitination pathways, phagosomal escape, and actin-cytoskeleton rearrangement processes.
authors.affiliation: Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, Maryland 21702;
authors.forename: Vesna
authors.initials: V
authors.lastname: Memisević
authors.forename: Nela
authors.initials: N
authors.lastname: Zavaljevski
authors.forename: Rembert
authors.initials: R
authors.lastname: Pieper
authors.forename: Seesandra V
authors.initials: SV
authors.lastname: Rajagopala
authors.forename: Keehwan
authors.initials: K
authors.lastname: Kwon
authors.forename: Katherine
authors.initials: K
authors.lastname: Townsend
authors.forename: Chenggang
authors.initials: C
authors.lastname: Yu
authors.forename: Xueping
authors.initials: X
authors.lastname: Yu
authors.forename: David
authors.initials: D
authors.lastname: DeShazer
authors.forename: Jaques
authors.initials: J
authors.lastname: Reifman
authors.forename: Anders
authors.initials: A
authors.lastname: Wallqvist
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D042726:Burkholderia mallei / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D005260:Female; D054884:Host-Pathogen Interactions / Q000235:genetics / Q000502:physiology*; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D016254:Mutagenesis, Insertional; D025941:Protein Interaction Mapping; D040901:Proteomics; D020798:Two-Hybrid System Techniques; D014774:Virulence / Q000235:genetics / Q000502:physiology; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D037521:Virulence Factors